Photographic materials may utilize filter dyes for a variety of purposes. Filter dyes may be used to adjust the speed of a radiation-sensitive layer; they may be used as absorber dyes to increase image sharpness of a radiation-sensitive layer; they may be used as antihalation dyes to reduce halation; they may be used reduce the amount or intensity of radiation from reaching one or more radiation-sensitive layers, and they may also be used to prevent radiation of a specific wavelength or range of wavelengths from reaching one or more of the radiation-sensitive layers in a photographic element. For each of these uses, the filter dye(s) may be located in any number of layers of a photographic element, depending on the specific requirements of the element and the dye, and on the manner in which the element is to be exposed. The amount of filter dyes used varies widely, but they are preferably present in amounts sufficient to alter in some way the photographic response of the element. Filter dyes may be located in a layer above a radiation-sensitive layer, in a radiation-sensitive layer, below a radiation-sensitive layer, or in a layer on the opposite side of the support from a radiation-sensitive layer.
Photographic materials often contain layers sensitized to different regions of the spectrum, such as red, blue, green, ultraviolet, infrared, X-ray, to name a few. A typical color photographic element contains a layer sensitized to each of the three primary regions of the visible spectrum, i.e., blue, green, and red. Silver halide used in these materials has an intrinsic sensitivity to blue light. Increased sensitivity to blue light, along with sensitivity to green light or red light, is imparted through the use of various sensitizing dyes adsorbed to the silver halide grains. Sensitized silver halide retains its intrinsic sensitivity to blue light.
There are numerous applications for which filtration or absorbance of very specific regions of light are highly desirable. Some of these applications, such as yellow filter dyes and magenta trimmer dyes, require non-diffusing dyes which may be coated in a layer specific manner to prevent specific wavelengths of light from reaching specific layers of the film during exposure. These dyes must have sharp-cutting bathochromic absorbance features on the bathochromic side to prevent light punch through without adversely affecting the speed of the underlying emulsions. Preferably these dyes should exhibit high extinction coefficients, and sharp-cutting bathochromic absorption edges when incorporated into photographic elements. Typically, to achieve these properties, solutions of dissolved, monomeric dyes have been incorporated. Dyes introduced by this method cannot be coated in a layer specific manner without the use of mordants, and therefore they often wander into adjacent layers and can cause problems such as speed loss or stain. Solubilized monomeric dyes may be mordanted to prevent wandering through adjacent layers. While the use of polymeric mordants can prevent dye wandering, such mordants aggravate the stain problem encountered when the dye remains in the element through processing.
Just as yellow filter dyes prevent false color rendition from the exposure of emulsions sensitized to a region of the spectrum other than blue filter dyes absorbing in the UV, magenta, cyan and infrared regions can prevent false color rendition by shielding sensitized emulsion layers from exposure to specific wavelength regions. One application of this strategy is the use of green-absorbing magenta trimmer dyes. In one type of typical color photographic element containing a layer sensitized to each of the three primary regions of the visible spectrum, i.e., blue, green, and red, the green-sensitized layer is coated above the red-sensitized layer and below the blue-sensitized layer. Depending on the chosen spectral sensitivity maxima for the sensitized silver halide layers, there may be a region of overlap between the spectral sensitivities of the green and red emulsions. Under such circumstances, green light which is not absorbed by the green-sensitive emulsion can punch through to the red sensitive emulsion and be absorbed by the leading edge of the red spectral sensitizing dye. This crosstalk between the green and red emulsions results in false color rendition. It would, therefore, be highly desirable to find a green-absorbing filter dye which upon incorporation into a photographic element would absorb strongly around the spectral maximum of the green-sensitized emulsion, and possess a sharp cutting bathochromic absorbance such that there is no appreciable absorbance just bathochromic to its absorbance maximum. Though the position of optimal absorption maximum for a magenta trimmer dye will vary depending on the photographic element being constructed, it is particularly desirable in one type of typical color photographic element containing a layer sensitized to each of the three primary regions of the visible spectrum, i.e., blue, green, and red, that a magenta trimmer dye absorb strongly at about 550 nm, and possess a sharp cutting bathochromic absorbance such that there is no appreciable absorbance above about 550 nm. Therefore it would be desirable to provide a filter dye for use in photographic elements that possesses high requisite absorbance in the green region of the spectrum below about 550 nm, but little or no absorbance above about 550 nm, and furthermore does not suffer from incubative or post process stain problems, and furthermore is not prone to migration in the coated film, but is fully removed upon processing.
One method used to incorporate soluble monomeric filter dyes into photographic film element layers is to add them as aqueous or alcoholic solutions. Dyes introduced by this method are generally highly mobile and rapidly diffusing and often wander into other layers of the element, usually with deleterious results. While the use of polymeric mordants can prevent dye wandering, such mordants aggravate the stain problem encountered when the dye remains in the element through processing.
Many filter dyes, of various hues, for use in photographic elements suffer from stain problems. Some dyes are not fully decolorized or removed during photographic processing, thus causing post processing stain. Filter dyes incorporated as latex dispersions are especially prone to post-process stain problems. Other dyes wander into other layers of the element, adversely affecting image quality. Dyes immobilized with cationic mordants are especially prone to wandering within the photographic element. Still other dyes react before exposure with other components of the photographic element, such as color couplers, thus causing incubative stain.
Green-absorbing filter dyes are also useful as antihalation dyes and as anticrossover dyes in X-ray films sensitive to green-emitting phosphors. A description of green absorbing anticrossover dyes for radiographic elements appears in U.S. Pat. Nos. 4,900,652 and 4,803,150.
Green-absorbing filter dyes incorporated as microcrystalline dye dispersions have been developed to address some of the problems of dye wandering and stain. U.S. Pat. Nos. 4,950,586; 4,948,717; 4,940,654; 4,923,788; 4,900,653; 4,803,150; 4,994,356; 5,098,820; 5,260,179; 5,283,165; 5,399,690; 4,861,700; 4,857,446; 4,855,221; 5,213,956; 5,213,957 and EP 430,186 disclose the use of various dyes in solid particle dispersions. However, in general, these dyes are broad and often exhibit unwanted absorption in the red region of the spectrum. The exact range of desirable absorbance for a green-absorbing filter dye can vary depending on the photographic element being designed for use. However, in one type of typical color photographic element in which a filter dye will be coated above a red-sensitive layer, it is desirable for the dye to exhibit high absorbance in green region of the spectrum below around 550 nm, and possess a sharp cutting bathochromic absorbance such that there is no appreciable absorbance past 550 nm. Many green-absorbing microcrystalline dyes which do not absorb in the red region of the spectrum are too hypsochromic to provide adequate absorption in the longer wavelengths of the green region.